When performing the installation of Shavlik Protect 9.1, Patch 1 (9.1.4446.0) you receive the following error:
Windows Installer - The upgrade patch cannot be installed by the Windows Installer service because the program to be upgraded may be missing, or the upgrade patch may update a different version of the program. Verify that the program to be upgraded exists on your computer and that you have the correct upgrade patch.
The improper installer package is being run on the system. Most likely you are attempting to use the patch installer (intended when you already have version 9.1 installed) on a system with Protect 9.0 installed.
Use the correct installer package to update your current version of Protect. Below is a listing of the installer for Protect 9.1.4446.0 that should be used for the corresponding version of Protect:
Currently on 9.0.x - Use full 9.1.4446.0 Installer package (84MB), found here.
Currently on 9.1.4334.0 - Use 9.1.4446.0 Patch Installer (17MB), found here.
Shavlik Protect 9.x